The invention relates to an identifier token comprising a token body, electronic circuitry embedded in said body, access means for bidirectionally and electronically accessing said circuitry on an external interface, and said circuitry encompassing identifier code means. Such identifier tokens have been realized for various purposes, such as for banking and other financial services, access control to physical spaces, conditional logical access to information services, and as an identifier key to apparatus such as motor cars and computer terminals. The identifier code has been realized in various ways as well, in particular by means of storing such codes in an internal memory that is only internally accessible for confronting with an externally presented password that in some way is transmitted to the token. An example of such token has been disclosed in U.S. Pat. No. 4,256,955 to Giraud.
The storing of a unique code into an integrated circuit means requires that the circuit, at least up to a certain instant, must have a memory write facility. This necessitates particular circuit features. Secondly, a tight security organization is required for keeping the actual code secret, because the time interval between writing the code in a hitech manufacturing environment and the ultimate delivery to a customer can be great. On the other hand, the security that is used expressed as the number of possible different codes or coding space is extremely variable, from many millions in finance, to a few hundred for lowsecurity applications. The cost of coding and code protecting must be commensurate to the financial advantages of the individualization of the tokens.